Roberts, 22, donned a mask and opened fire with a AR-15 semiautomatic weapons at a Portland-area mall on Tuesday, killing two people before committing suicide, according to the Clackamas County sheriff.

"I don't understand," Hannah Patricia Sansburn, 20, tells ABC News. "I was just with him. I just talked to him. I didn't believe it was him at all. Not one part of me believed it."

She says he recently quit his job at a Portland sandwich shop and sold all his possession, telling her that he was moving to Hawaii. He was supposed to take a flight Saturday but told her he got drunk and missed it.

"And then this happens ... it makes me think, was he even planning on going to Hawaii?" Sansburn says.

She says the couple had dated for nearly a year before breaking up over the summer and she had never seem him act violently or get angry.

"Jake was never the violent type. He didn't go out of his way to try to hurt people or upset people. His main goal was to make you laugh, smile, make you feel comfortable. I never would have guessed him to do anything like this ever," she tells ABC.

Sansburn says, however, that he "seemed numb" when she saw him for the last time last week.

In her last text message, she told Roberts she didn't want him to leave. He replied: "I'm sorry," with a sad face emoticon.

One of his former neighbor's said Roberts liked to play video games and never seemed troubled, the Associated Press reported.

"He was like a rapper. He would rap all the time," said Samantha Bennett, who lived across the hall from Roberts at an apartment complex in 2011.